Interestingly, the commentary on Article 85 of the Third Geneva Convention includes “the wearing of civilian clothing by members of the armed forces for purposes of disguise” as an example of a war crim
Bonus points because guess where I read that?
https://en.idi.org.il/media/6191/combatants_dressed_as_civilians.pdf
It seems like some things just don’t change.
It’s slang for military butt sex.